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A simple, stable, and high-sensitivity temperature sensor based on multimode interference in a polymer optical fiber (POF) with higher-order mode excitation has been developed. In a single-mode–multimode–single-mode (SMS) structure, one end of the multimode POF with physical-contact (PC) connectors is connected to a silica single-mode fiber with an angled-PC (APC) connector. We compare the temperature sensing characteristics of the three configurations (no PC-APC, PC-APC at input, and PC-APC at output) and obtain the highest temperature sensitivity of 219.2 pm °C−1, which is more than double the value of the standard (no PC-APC) SMS structure. [ABSTRACT FROM AUTHOR]

Daily changes in light and temperature are major entrainment cues that enable the circadian clock to generate internal biological rhythms that are synchronized with the external environment. With the average global temperature predicted to keep increasing, the intricate light–temperature coordination that is necessary for clock functionality is expected to be seriously affected. Hence, understanding how temperature signals are perceived by the circadian clock has become an important issue. In Arabidopsis, the clock component EARLY FLOWERING 3 (ELF3) not only serves as a light Zeitnehmer , but also functions as a thermosensor participating in thermomorphogenesis. However, the role of ELF3 in temperature entrainment of the circadian clock is not fully understood. Here, we report that ELF3 is essential for delivering temperature input to the clock. We demonstrate that in the absence of ELF3 , the oscillator is unable to respond to temperature changes, resulting in an impaired gating of thermoresponses. Consequently, clock-controlled physiological processes such as rhythmic growth and cotyledon movement were disturbed. Genetic analyses suggest that the evening complex is not required for ELF3 -controlled thermoresponsiveness. Together, our results reveal that ELF3 is an essential Zeitnehmer for temperature sensing of the oscillator, and thereby for coordinating the rhythmic control of thermoresponsive physiological outputs. [ABSTRACT FROM AUTHOR]

Organic persistent luminescent materials attract great attention, but most of them exhibit single luminescence color with one emission band, which limits their applications in optoelectronic, sensing, and bioimaging fields. Herein, an effective strategy to achieve dual persistent emission is proposed by utilizing the triplet excited state in the single‐molecule 6,12‐diphenyl‐5,6,11,12‐tetrahydroindolo[3,2‐b]carbazole derivatives. Experimental data and theoretical calculations suggest that the triplet excited state operates as a triplet exciton reservoir to stockpile and provide long‐lived excitons for room temperature phosphorescence (RTP) and thermally activated delayed fluorescence (TADF) in aggregate state. Moreover, tunable emission color is achieved through the regulation of RTP and TADF emission by introducing aromatic and aliphatic bromine atoms. Finally, dual persistent emission with a long lifetime of 0.26 s and a persistent luminescence quantum yield of 10% is obtained in single‐component materials, and these luminophores are used for visual temperature detection and anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

[Display omitted] The right choice of synthesis route for upconverting nanoparticles (UCNPs) is crucial for obtaining a well-defined product with a specific application capability. Thus we decided to compare the physicochemical, cytotoxic, and temperature-sensing properties of UCNPs obtained from different rare earth (RE) ions, which has been made for the first time in a single study. The core/shell NaYF 4 :Yb3+,Er3+/NaYF 4 UCNPs were obtained by reaction in a mixture of oleic acid and octadecene, and their highly stable water colloids were prepared using the ligand-free modification method. Both oleate-capped and ligand-free UCNPs exhibited a bright upconversion emission upon 975 nm excitation. Moreover, slope values, emission quantum yields, and luminescence lifetimes confirmed an effective energy transfer between the Yb3+ and Er3+ ions. Additionally, the water colloids of the UCNPs showed temperature-sensing properties with a good thermal sensitivity level, higher than 1 % K−1 at 358 K. Evaluation of the cytotoxicity profiles of the obtained products indicated that cell viability was decreased in a dose-dependent manner in the analyzed concentration range. [ABSTRACT FROM AUTHOR]

Temperature is a key parameter in most biological and physical systems. It is, however, an inherent technological challenge to precisely track and control the temperature of small sample volumes when using high- and super-resolution microscopes. Various effects can cause a deviation of the sample temperature from its expected value, specifically in the observed volume or field-of-view. These effects include direct thermal contact of the objective lens and the coverslip via immersion medium, illumination-induced heating, evaporative cooling, or triggered phase transitions. In this paper, we shed light on these phenomena and introduce our newly developed device VAHEAT, which follows a microscopic approach for controlling and measuring the sample temperature. Our system overcomes traditional limitations of temperature sensing and controlling in high-sensitivity microscopy applications, leading to more reproducible experimental results and conquering new experimental parameter ranges. [ABSTRACT FROM AUTHOR]

In the field of physical oceanography, the temperature and pressure of seawater are important fundamental parameters. In order to realize the simultaneous measurement of the temperature and pressure in seawater, a reflective optical fiber sensor based on polydimethylsiloxane (PDMS)-sealed optical microfiber coupler combined with a sagnac loop (OMCSL) is proposed. Benefiting from the high thermo-optical coefficient and large elasticity of PDMS, and the large-scale swift field transmission characteristics of optical microfiber coupler (OMC), the sensitivity and structural stability of our sensor is largely improved. The response performance of the sensor is further analyzed by numerical simulation calculations and theoretical modeling. Experimental results show that the temperature and pressure sensitivity of the sensor could reach −2.133 nm/°C and 3.416 nm/Mpa, respectively, about one order higher than that of bare fiber OMCSL. Furthermore, via inversely calculating the cross-sensitivity matrix, the temperature and pressure sensing can be demodulated simultaneously, and the average errors of the preliminary experimental settlements are 1.61% and 5.02%, respectively. Due to the merits of compact structure, easy fabrication, high sensitivity, fast response speed and high stability, the basic performance of this dual parametric sensor is comparable to the existing electrical temperature-depth (TD) sensor, which is expected to meet the practical application requirements of marine environmental monitoring and ocean dynamics research. [ABSTRACT FROM AUTHOR]

[Display omitted] • A skin-inspired thermoelectric nanocoating was constructed. • The nanocoating exhibited accurate temperature sensing at 100–300 ℃. • The nanocoating exhibited sensitive and repeatable fire-warning capability. • The nanocoating significantly improved the flame retardancy of many combustible materials. Temperature sensing enables flammable materials to respond intelligently at high temperature, which is conducive to further improving their fire safety. However, it is still challenging to develop a smart nanocoating with sensitive temperature-sensing and efficient flame retardancy. Inspired by human skin, a thermoelectric flame retardant (TE-FR) nanocoating was fabricated by combining a dermis-mimicking thermoelectric (TE) layer and an epidermis-mimicking flame retardant (FR) layer. The TE-FR nanocoating exhibited accurate temperature sensing at 100–300 ℃ and repeatable fire-warning capability. When being burned, the fire-warning response time of the TE-FR nanocoating was only 2.0 s, and it retriggered the fire-warning device within 2.8 s when it was reburned. Meanwhile, the TE-FR nanocoating exhibited outstanding flame retardancy. The coated polypropylene self-extinguished in the horizontal and vertical burning tests. Besides, its peak heat release rate, total heat release, and peak smoke production rate were significantly reduced. This work proposed an ingenious strategy to fabricate smart nanocoating for temperature sensing and fire safety, which revealed an enticing prospect in the fields of fire protection, electronic skin, and temperature monitor. [ABSTRACT FROM AUTHOR]

A simply fabricated, highly sensitive, and inexpensive optical fiber temperature sensor is reported with a Fabry–Perot (FP) microcavity of controlled length. The microcavity with controllable length is fabricated by single-mode fiber (SMF) and polydimethylsiloxane (PDMS) for temperature sensing. After the PDMS is cured, the SMF is connected to the supercontinuum light source (SCLS) and the optical spectrometer analyzer (OSA) for online observation of the reflection spectrum. The micro-displacement platform is used to pull the SMF to form an air cavity. After the air cavity is stabilized, ultraviolet (UV) activated glue is used for packaging outside the PDMS. The FP microcavity is formed by the end face of the SMF and the face of PDMS. The length of the FP microcavity can be controlled online by the micro-displacement platform to a minimum of 15 µm. The free spectral range (FSR) may reach 74.8 nm and the interference fringe contrast (IFC) is up to 19.8 dB to allow sensitive measurements across a wide temperature range. The experiments demonstrate a high temperature sensitivity of 5.388 nm/°C from 33 to 93 °C with high repeatability and linearity (R2=0.9937). Stability experiments showed that the maximum changes in wavelength and intensity are only 45 pm and 0.035 dB, respectively. It is anticipated that the easily constructed, compact, and inexpensive fiber-optic temperature sensor will be employed in practical applications. [ABSTRACT FROM AUTHOR]

Light with wavelength longer than 1500 nm has great potential to afford deep bio‐tissue penetration due to its extremely weak photon scattering and undetectable autofluorescence in vivo. Here, in order to satisfy the requirements for thermometry during the tumor hyperthermia process, an ultrasensitive optical thermometer operating beyond 1500 nm is developed by employing the thermally coupled Stark sublevels of Er3+: 4I13/2 → 4I15/2 transition based on fluorescence intensity ratio (FIR) technology in Yb3+ and Er3+ codoped BaY2O4. Compared with the typical upconversion (UC) material β‐NaYF4: Yb3+/Er3+ and Y2O3: Yb3+/Er3+, BaY2O4: Yb3+/Er3+ shows more intense red Er3+: 4F9/2 → 4I15/2 transition and 1.5 μm near‐infrared (NIR) Er3+: 4I13/2 → 4I15/2 transition induced by its larger phonon energy and higher quenching concentration of Er3+. An equivalent four‐level model is proposed to investigate the temperature characteristics of the NIR emission, from which four Stark transitions are separated from the raw spectra, named α, β, γ, and δ respectively. Then, the NIR thermal sensing performance have been developed by utilizing the FIR of Iβ to Iα and Iγ to Iα. More importantly, an ultra‐high sensitivity for optical thermometry has been obtained through the combination of transition β and γ, especially in the physiological temperature region. Furthermore, the detection depth of NIR light in bio‐tissues is assessed by an ex vivo test, demonstrating that the maximal detection depth of NIR emission can reach to 8 mm without any influence on optical thermometry. These findings indicate that Yb3+ and Er3+ codoped BaY2O4 is a remarkable contender for optical thermometry in deep tissue with ultra‐high sensitivity. [ABSTRACT FROM AUTHOR]

Luminescent thermometry is a noninvasive method of temperature detection with high sensitivity and response speed. The present study demonstrated the process‐intensified synthesis of ytterbium and erbium codoped calcium molybdate phosphors (CaMoO4:Yb3+/Er3+). The experiment involved the initial premixing of the precursors using a high‐gravity rotating packed bed (RPB) reactor and subsequent calcination processing. The pronounced mass transfer and micromixing of the reactants in the RPB facilitated the scalable and controllable synthesis of CaMoO4:Yb3+/Er3+ particles with submicron sizes and regular morphologies. The CaMoO4:Yb3+/Er3+ particles exhibited a bright‐green emission with temperature‐dependent luminescence characteristics under 980 nm laser irradiation. Furthermore, the maximum absolute sensitivity was determined to be 0.02837 K−1. These results indicated that the synthesized product was a suitable candidate for application in upconversion luminescent thermometers capable of temperature sensing at the microscale. [ABSTRACT FROM AUTHOR]

Fano resonance effect has potential applications in many nanophotonics devices, Such as switch, sensor, and modulators. To realize double Fano resonance effect, in this paper, we present a novel coupling mechanism in a multi-layer metamaterial structure. The structure consists of periodic TiO2 grating covered with MgF2-TiO2-Ag multilayer with a MgF2 substrate. Results show that one of the two Fano resonance is caused by the interference between a broad Fabry-Perot (FP) mode and a dark waveguide mode (WG), and the other Fano resonance is caused by the asymmetric waveguide mode of the MgF2-TiO2-Ag layer. The effect of structural parameters on transmission is also studied, the field distribution of the proposed nanostructure is presented to illustrate the mechanism. We achieve a refractive index sensitivity of 73.5 nm/RIU, and temperature sensitivity of 0.0915nm/°C, the ultra-narrow transmission bandwidth leads to the high FOM*. The results will pave the way towards the design of double band Fano resonance, which may have potential application in high signal-to-noise ratio measurement, plasmonic modulator and refractive index sensor or temperature sensor.

Polypropylene (PP) remains the primary material for hernia meshes due to its biocompatibility, physical strength and ease of fabrication. However, PP meshes are still subject to complications such as mesh movement and bacterial infection that ultimately lead to mesh failure. This study describes a two-step functionalization of a PP mesh through dopamine-mediated chloro(triphenylphosphine)gold(I)/nanodiamond coatings. The gold compound provided an intrinsic surface with antimicrobial activity to the coatings, whilst the overall improvement in hydrophilicity and roughness allows for efficient adsorption of antibiotics with an aim for eradicating bacteria in the surrounding tissue. The presence of a gold compound on the surface of the mesh enhanced its contrast property, which may provide a surgical application to determine the ease of monitoring the PP mesh location after implantation inside the body to detect possible tears. Photostable negatively charged nitrogen-vacancy centres within the nanodiamonds provides an exciting possibility to optically assess locally elevated temperatures often associated with infection or excessive inflammation. The biocompatibility, antibiotic loading and associated antimicrobial properties of the coated mesh were investigated to show the potential of this new coating for future applications in hernia surgical procedures.

A novel method for ultra-sensitive and ultra-fast temperature sensing has been successfully implemented by cascading Saganc rings to generate the Vernier effect and doing the same dispersive fibers to achieve the optical time-stretching effect. This is different from the traditional point fiber sensor demodulated by optical spectrum analyzer (OSA) whose demodulation speed is usually at the second level. The designed system maps the wavelength domain to the time domain through the dispersive fiber, which can realize the ultra-fast temperature monitoring at the nanosecond level. The cascaded Sagnac ring is composed of polarization maintaining fiber (PMF) which is significantly affected by the thermal-optical coefficient. When the temperature changes, the variation is as high as −6.228 nm/°C, which is 8.5 times higher than the sensitivity based on the single Sagnac ring system. Furthermore, through the optical time stretching scheme, the corresponding response sensitivity is increased from 0.997 ns/°C to 7.333 ns/°C, and the magnification is increased 7.4 times with a response speed of 50 MHz.

High precision temperature measurements are a transversal need in a wide area of physical experiments. Space-borne gravitational wave detectors are a particularly challenging case, requiring both high precision and high stability in temperature measurement. In this contribution, we present a design able to reach 1 μK/Hz in most of the measuring band down to 1 mHz, and reaching 20 μK/Hz at 0.1 mHz. The scheme is based on resistive sensors in a Wheatstone bridge configuration which is AC modulated to minimize the 1/f noise. As a part of our study, we include the design of a test bench able to guarantee the high stability environment required for measurements. We show experimental results characterising both the test bench and the read-out, and discuss potential noise sources that may limit our measurement.

We report on the development and implementation of an optical frequency-domain reflectometer (OFDR) sensing platform. OFDR allows to measure changes in strain and temperature using optical fibers with a length of several tens of meters with very high spatial resolution. We discuss the operation principles and challenges to implement an OFDR system using optical homodyne detection based on a dual-polarization 90° optical hybrid. Our setup exhibits polarization and phase diversity, fully automated data acquisition and data processing using a LabVIEW-based implemented software environment. Using an optical hybrid enables to discriminate phase, amplitude and polarization by interfering the Rayleigh scatter signal and a local oscillator with four 90° phase stepped interferences between the two signals. Without averaging and a fast acquisition time of 230 ms, our preliminary results show a spatial resolution of 5 cm and a temperature resolution of about 0.1 Kelvin on a 3 m-long fiber. [ABSTRACT FROM AUTHOR]

Hexagonal NaYF4: Er3+/Yb3+ (β‐NaYF4) microprisms with uniform particle sizes were synthesized via a microwave‐assisted hydrothermal method (MWHM). Nucleation and crystal growth were significantly surpassed owing to the microwave irradiation. Cubic‐NaYF4: Er3+/Yb3+ (α‐NaYF4) nanoparticles were transformed into β‐NaYF4 microprisms with reaction time in between 10 and 120 minutes at 180°C. The shape of the particles was enhanced via controlling the nucleation process with optimized irradiation duration and heating rates. The size distribution of β‐NaYF4 microprisms was further improved via regulating the concentration of chelating agents and pH values in the precursor solution. β‐NaYF4 microprisms displayed red and green color emissions for 980 nm excitation owing to the 4F9/2 and 2H11/2/4S3/2 → 4I15/2 transitions of Er3+ respectively. The ratio (2H11/2/4S3/2 → 4I15/2) between green fluorescence intensities (FIR) of β‐NaYF4 microprisms was recorded with the variation in temperature from 303 K to 550 K. The recorded FIR values obeyed Boltzmann distribution and the distribution was used to evaluate the sensitivity. The optimum absolute sensitivity was achieved as 0.0044 K−1 at 490 K with promising resolution, reversibility, and stability. Furthermore, the power‐dependent variations in FIR values implied the suitability of β‐NaYF4 microprisms in measuring the laser‐induced heating effects. [ABSTRACT FROM AUTHOR]

Design and investigation of a polarization-insensitive nine-band tunable metamaterial absorber at THz frequencies with equal to or more than 90% absorption ratio in all of the bands are reported. The tunable metamaterial absorber consists of four isosceles triangle patches with four U-shaped cut paths on top of an indium antimonide substrate, which has a fully metallic ground plane at the backside. Numerical analyses show that the metamaterial absorber has wide-angle characteristics under transverse-electric and transverse-magnetic modes. The permittivity of indium antimonide is highly dependent on temperature variations due to its temperature-dependent intrinsic carrier density, leading to shift of nine absorption peak frequencies upon change of environment temperature. Broadband switching of nine absorption peak frequencies with maximum 71.5% shift ratio between 190 K and 230 K is obtained. Temperature sensing performance of the metamaterial absorber is further evaluated and the sensitivities are found to be 11.5 GHz/K, 9.2 GHz/K, 8.3 GHz/K, 7.6 GHz/K, 7.0 GHz/K, 6.2 GHz/K, 5.3 GHz/K, 4.5 GHz/K and 4.2 GHz/K, from the first to ninth absorption band, respectively. Therefore, the proposed nine-band metamaterial absorber sensor has great potential in sensitive and accurate temperature measurement, absorption tuning in optoelectronic applications and as frequency selective thermal emitters. [ABSTRACT FROM AUTHOR]

Single phase Er3+ activated Na 2 CaSiO 4 (NCSO) phosphors were synthesized successfully via sol-gel technique. As-synthesized NCSO: Er3+ samples have been characterized using various techniques to explore crystallinity, morphology, photoluminescence (PL) features, thermal sensing properties and thermal stability. An intense green emission peak has been observed at 558 nm under 379 nm (near-UV) excitation for NCSO: Er3+ phosphors. Moreover, the Er3+ ions concentration has been optimized at 6.0 mol% in NCSO host lattice to achieve maximum intensity, beyond which the emission intensity reduces due to concentration quenching. Temperature-dependent PL studies indicate excellent thermal stability as the emission intensity persists up to 71% and 66% of the room temperature intensity at 383 K and 423 K, respectively. The chromaticity coordinates (0.328, 0.654) under 379 nm excitation for the optimized NCSO: Er3+ phosphor situated in the green region. Further, the superior temperature sensing behaviour of the proposed phosphor is highly expected from the obtained relative sensitivity value of 1.88% K−1. Above mentioned results indicate the potentiality of the green emitting NCSO: Er3+ phosphor for multifunctional optoelectronic devices. [ABSTRACT FROM AUTHOR]

Optical thermometry and white light-emitting diodes (WLEDs) are the research hotspots for Eu3+ doped phosphors. In this study, a series of Sr 2 TiSi 2 O 8 : Eu3+ red phosphors were developed in a solid-state reaction method. The luminescent properties of the Sr 2 TiSi 2 O 8 : Eu3+ phosphor illustrate that Sr 2 TiSi 2 O 8 : Eu3+ is effectively excited by the NUV LED chip and emit an intense red light with a peak of 618 nm due to the noninversion symmetry coordination of Eu3+ in Sr 2 TiSi 2 O 8. The local coordination environment of Eu3+ was investigated in detail using crystallographic data, spectroscopic data and Judd–Ofelt parameters. In addition, the emission intensity of Sr 2 TiSi 2 O 8 :Eu3+ is extremely sensitive to temperature. The relative sensitivity of Sr 2 TiSi 2 O 8 :Eu3+ is 1.1% k-1@300 k, which is comparable to other Eu3+-activated temperature sensing materials. The possible mechanism of the temperature sensitive quenching characteristics was proposed. The results indicate that Sr 2 TiSi 2 O 8 :Eu3+ is a potential temperature sensing material. [ABSTRACT FROM AUTHOR]

A novel Mach-Zehnder interferometer (MZI) with thin core fiber (TCF) – polarization-maintaining photonic crystal fiber (PMPCF) structure for measurement of temperature and strain is proposed and demonstrated experimentally. The MZI is formed by splicing a section of TCF and a section of PMPCF with core offset between two sections of single mode fibers (SMFs). Three sensors with different PMPCF lengths are investigated and compared. Since cladding modes and core mode respond differently to temperature and strain changes, both values can be measured independently. The temperature and strain sensitivities can be achieved simultaneously through the demodulation matrix. For the wavelength-related measurement, the temperature and strain sensitivities are 8.81 pm/°C and 2.98 pm/µε, respectively. In addition, the influence of temperature cross-sensitivity is also analyzed. The proposed sensor offers several advantages such as low cost, simple manufacturing technology, and temperature insensitiveness, which can be further applied in practical sensing. [ABSTRACT FROM AUTHOR]

A distributed temperature monitoring inside a cavity of ytterbium DFB and holmium fiber lasers has been demonstrated with a spatial resolution of 1 and 5 mm, respectively, for the first time to the best of our knowledge. For this, we use an optical backscatter reflectometer, which measures intracore temperature, and compare it with the data of an IR thermographic camera, which measures temperature from the surface of a fiber. In the case of holmium fiber laser pumped at a wavelength of 1125 nm with a power of 6 W, the maximum temperature variation along the ∼3-m active fiber reaches ∼60 °C. In the case of ytterbium DFB laser, we observe a strong inhomogeneity of the temperature along the DFB cavity, which leads to a significant decrease in the lasing efficiency. When pumped by a single-mode laser diode at a wavelength of 976 nm with a power of up to 526 mW, the maximum temperature difference reaches 37 °C for the 37-mm DBF cavity. [ABSTRACT FROM AUTHOR]

The transparent Er3+‐Yb3+‐doped fluoro‐aluminosilicate glass‐ceramic (GC) was prepared by melt‐quenching. The crystal phase, morphology, and up‐conversion (UC) luminescence of as‐produced GC were characterized by X‐ray diffraction, scanning electron microscopy, and fluorescence spectrophotometry, respectively. The results show that BaYF5 nanocrystals were uniformly distributed in the glass matrix of the as‐produced GC. When the as‐produced GC was subjected to heat treatment, the crystallinity was increased, but the crystal identity remains unchanged. Such heat‐treatment doubled the intensity of the UC luminescence, and this enhancement was ascribed to the increased incorporation of both Er3+ and Yb3+ ions into the lower phonon energy environment of BaYF5 nanocrystals. Furthermore, the heat‐treated GC was stable against further crystallization, and consequently its UC luminescence was stable at the application temperature. The heat‐treated GC was found to possess an outstanding temperature‐sensing capability. [ABSTRACT FROM AUTHOR]

We design high-sensitive fiber-optic sensor based on modal interference for temperature measurements. The core mismatch-offset sensor is fabricated by splicing a section of multimode fiber (MMF) between two single-mode fiber (SMF) and offset splicing of SMF. We use the finite-difference beam propagation method to numerically analyze the mode and intensity distributions of the light field in the sensor. We optimize the structure parameters such as the length of MMF, the length of sensing SMF, and the offset of sensor; the optimum parameters of proposed sensor are 4.0 mm, 1.73 cm, and 3.5 μm, respectively. Experimental results show that the proposed sensor is successfully used to monitor the variation of ambient temperature, and it possesses a high temperature sensitivity of 167.2 pm/°C with good linearity. The core mismatch-offset sensor with high sensitivity and compact structure provides a new method for designing fiber-optic sensor and temperature sensing. [ABSTRACT FROM AUTHOR]

A transparent ferroelectric 0.75Pb(Mg 1/3 Nb 2/3)O 3 -0.25PbTiO 3 :0.015Pr3+ ceramic was synthesized and its temperature-sensing ability was investigated based on the fluorescence intensity ratio (FIR) method. The transparency was found to be of the order of 68% at 900 nm for a sample thickness of 0.7 mm, comparable to the theoretical value of ~71%, benefiting the photoluminescence of the Pr3+ ions inside the ceramic. Instead of the traditional Boltzmann exponential style and varying sensitivity, a highly linear temperature response was obtained for the studied ceramic. Further, a constant FIR sensitivity of 0.70 %K-1 was achieved over the temperature range of -50–40 °C, making the ceramic suitable for thermometry at room temperature and below. [ABSTRACT FROM AUTHOR]

Solar‐driven photothermal antibacterial devices have attracted a lot of interest due to the fact that solar energy is one of the cleanest sources of energy in the world. However, conventional materials have a narrow absorbance band, resulting in deficient solar harvesting. In addition, lack of knowledge on temperature change in these devices during the photothermal process has also led to a waste of energy. Here, we presented an elegant multi‐channel optical device with a multilayer structure to simultaneously address the above‐mentioned issues in solar‐driven antibacterial devices. In the photothermal channel, semiconductor IrO2‐nanoaggregates exhibited higher solar absorbance and photothermal conversion efficiency compared with nanoparticles. In the luminescence channel, thermal‐sensitive Er‐doped upconversion nanoparticles were utilized to reflect the microscale temperature in real‐time. The bacteria were successfully inactivated during the photothermal effect under solar irradiation with temperature monitoring. This study could provide valuable insight for the development of smart photothermal devices for solar‐driven photothermal bacterial inactivation in the future. [ABSTRACT FROM AUTHOR]

In this work, Lu 7 O 6 F 9 microcrystals with various novel morphologies, including hand broom-like nanorods, nanoparticles, hexagons, spindle-like nanoparticle aggregates, hexagonal prisms and microrods, were prepared via ionic liquid-assisted two-phase method and following calcination approach. Ionic liquid was used as F− resource, morphology controller and two-phase solvent. The effect of preparation condition on the phases and morphologies of the precursors as well as the calcined products was studied in detail. The crystallographic structure of Lu 7 O 6 F 9 was also confirmed by the down-conversion (DC) spectra of Lu 7 O 6 F 9 : Eu3+ phosphor with Eu3+ ion as the structure probe. Besides, different concentration of Yb3+ ions were introduced to the host to obtain Lu 7 O 6 F 9 : Yb3+, Er3+ phosphors, in case of subsequent investigation on the up-conversion (UC) luminescence properties, UC mechanism and followed temperature sensing behavior. Color-tunable UC emissions were realized and the mechanism was discussed. Furthermore, the optical temperature sensing behavior of orthorhombic Vernier lutecium oxyfluoride was investigated for the first time. The influence of Yb3+ content on the sensing sensitivity was also elaborated. These results imply that the as-prepared Lu 7 O 6 F 9 : Yb3+, Er3+ phosphors could be considered as candidates in color-tunable displaying and optical thermometers. [ABSTRACT FROM AUTHOR]

Plants dynamically adapt to changing temperatures to ensure propagation and reproductive success, among which morphogenic responses to warm temperatures have been extensively studied in recent years. As readily inferred from the cyclic co-oscillations of environmental cues in nature, plant thermomorphogenesis is coordinately reshaped by various external conditions. Accumulating evidence supports that internal and developmental cues also contribute to harmonizing thermomorphogenic responses. The external and internal reshaping of thermomorphogenesis is facilitated by versatile temperature sensing and interorgan communication processes, circadian and photoperiodic gating of thermomorphogenic behaviors, and their metabolic coordination. Here, we discuss recent advances in plant thermal responses with focus on the diel and seasonal reshaping of thermomorphogenesis and briefly explore its application to developing climate-smart crops. Multiple thermosensors and thermosensory mechanisms, including biophysical thermosensors, have distinct and overlapping roles in triggering an array of thermomorphogenic responses in plants. Diverse temperature signaling molecules are actively transmitted through interorgan communication routes to synchronize thermomorphogenic responses in plant organs. Plant thermomorphogenesis is precisely gated by the circadian clock to help plants stimulate thermos-adaptive behaviors at the most favorable time point of the day. Plants integrate daylength and temperature information into the circadian clock to aptly shape thermomorphogenic growth under diel and seasonal fluctuations. Plant thermomorphogenesis is extensively reshaped by endogenous metabolic signals, which largely depend on photosynthetic performance and soil environments. [ABSTRACT FROM AUTHOR]

In this work, it is proposed a novel customized-accuracy simultaneous sensing of temperature, pressure and acoustic impedance based on forward Brillouin scattering (FBS) in optical fiber. By observing the variations in frequency shift-temperature, frequency shift-pressure and frequency shift-acoustic impedance for different radial acoustic modes in certain types of fibers, we propose a novel method for simultaneously measuring three parameters (temperature, pressure and acoustic impedance) using the changes of frequency shift of three FBS scattering peaks. It is very interesting that we can utilize numerous sensitivity combinations of three measured parameters corresponding to different frequency shifts in optical fibers, allowing for the selection of different combinations of measurement accuracy for temperature, pressure and acoustic impedance sensing, and thus meeting the different requirements for measurement accuracy in specific measurement applications. In a proof-of-concept experiment, a 1060-XP fiber is used as the sensing fiber. By choosing suitable sensitivity combinations of coefficients of frequency shift-temperature, frequency shift-pressure and frequency shift-acoustic impedance of the fiber, we achieve high-accuracy simultaneous measurement of temperature, pressure and acoustic impedance with low measurement uncertainties of 0.13 °C, 0.04 MPa and 0.006 MRayl, respectively. The proposed method not only realize temperature, pressure and acoustic impedance simultaneous sensing for the first time, but also open up a new way of fiber optic sensing with customized multi-parameter sensing accuracy. [ABSTRACT FROM AUTHOR]

[Display omitted] • For the first time, the gel-to-liquid phase transition property of a hybrid niosome, made with span 60 and L64, is effectively utilized to design a FRET-based nanothermometer. • The ratio of the fluorescence signal of pyrene (donor) and coumarin 102 (acceptor) loaded in hybrid niosomes is used as the indicator for physiological temperature sensing. • The dye-loaded hybrid niosomes as temperature sensor displayed high reversibility for as many as twenty heating–cooling cycles in the temperature range 20–50 °C. • The obtained relative sensitivity (S r) of 9.4 % °C−1 at 42 °C with temperature resolution (δT) of 0.0016 °C is the best reported for any luminescent temperature sensor to date. • The sensor is suitable for visual detection and its performance is intact across various pH and under increasing ionic strengths. Optical thermometers relying on fluorescence intensity are indispensable due to their high sensitivity, non-contact temperature sensing capability, and exceptional repeatability. In this study, we introduce fluorescence resonance energy transfer (FRET)-based ratiometric temperature sensing utilizing pyrene (as the donor) and coumarin 102 (as the acceptor) loaded into hybrid niosomes composed of non-ionic surfactant span 60 (S60) and pluronic copolymer L64. Under 335 nm excitation, with an increase in temperature from 20 °C to 50 °C, the fluorescence emission intensity of pyrene decreases, while that of coumarin 102 (C102) increases, enabling ratiometric temperature detection within the physiological range. This reversible phenomenon is primarily attributed to the phase transition of the hybrid niosomes from the gel phase to the liquid phase. The fluorescence intensity ratio (FIR), calculated as the emission intensity of pyrene at 394 nm to the emission intensity of C102 at 469 nm, serves to determine the relative sensitivity of the sensor. Remarkably, the sensor exhibits a relative sensitivity of 9.4 % °C−1, with a temperature resolution of 0.0016 °C at 42 °C, ranking among the best values reported thus far. These findings highlight the potential of the designed pyrene-C102-loaded hybrid niosomes for optical temperature sensing applications, particularly in disease detection within the physiological range (20–50 °C). [ABSTRACT FROM AUTHOR]

Lanthanide upconversion luminescent materials featuring multi-peak and tunable emissions allow for ratiometric luminescence thermometry in a remote detection manner. However, wide explorations are still required to develop relevant materials for efficient thermometric performances. Herein, Yb3+/Er3+ co-doped non-stoichiometric analogues of bismuth oxyfluoride were obtained by simply tuning the F−/(Bi3+ + Ln3+) molar ratio of the reactants in a solid-state reaction method, for the first time. We achieved simultaneous regulations in composition, structure, morphology, and upconversion luminescence properties of BiO x F y :Yb/Er (2/1 mol%) microcrystals. Compositional analysis revealed not only the predictable increase of fluorine content, but also the constant O/(Bi + Ln) atomic ratios in all nominal BiO x F y :Yb/Er. Experimental results showed the structure and morphology evolutions from hexagonal-phase micro-flowers, to tetragonal-phase microplates, and further to orthorhombic-phase irregular microcrystals. Benefiting from adjustable composition, structure and morphology, up-conversion luminescence with adjustable intensity and color was obtained. Temperature dependent upconversion properties and ratiometric thermometric performances based on the thermally coupled levels, 2H 11/2 and 4S 3/2 of Er3+, were explored. BiOF:Yb/Er, BiO 0.67 F 1.66 :Yb/Er, and BiF 3 :Yb/Er microcrystals were found as suitable temperature sensing candidates with operating temperature range as wide as 298−673/723 K, high relative sensitivity up to 1.24% K-1, and minimum temperature uncertainty of 0.15 K. These results benefit not only further explorations for high-performance lanthanide-based luminescence thermometers, but also the chemistry of fluorides made from the solid-state reaction method. [Display omitted] • Non-stoichiometric analogues of BiOF obtained by controlling the amount of NH 4 F. • Evolutions in structure and morphology of BiO x F y :Yb/Er were revealed. • O/(Bi + Ln) atomic ratios remain constant in all nominal BiO x F y :Yb/Er. • BiO x F y :Yb/Er show intensity-varied and multicolor upconversion luminescence. • BiO x F y :Yb/Er permit wide temperature detection range, high S r and low uncertainty. [ABSTRACT FROM AUTHOR]

• We developed a high-speed Raman temperature sensor with enhanced compatibility with existing strain sensors. • We revealed that the optimal Raman power measurement frequency is ∼195 THz, near the Rayleigh peak, not the traditional 206 THz. • We demonstrated effective real-time temperature sensing by monitoring Raman power variations at this specific frequency. This paper presents a high-speed Raman temperature sensor that is highly compatible with current strain sensors. Challenging conventional assumptions, we found that at a communication wavelength of 193 THz, the optimal frequency for measuring Raman scattering power is not the typically dominant 206 THz, linked to stimulated Raman scattering, but rather around 195 THz, in proximity to the Rayleigh scattering peak. Our study demonstrates the effectiveness of real-time temperature sensing through the monitoring of power fluctuations in Raman scattering at this particular frequency. © 2024 Elsevier Science. All rights reserved. [ABSTRACT FROM AUTHOR]

Rare earth doped fluoride-based up-conversion luminescent materials have been widely studied in non-contact temperature sensing technology. However, the luminous intensity of the fluoride at high temperature still needs to be improved. Here, enhanced up-conversion luminescence and temperature sensing performance of NaBiF 4 : Er3+, Yb3+ is realized by Al3+ substitution. The samples exhibit the characteristic green (521 nm and 540 nm) and red (654 nm) emissions of Er3+ ion under 980 nm excitation. When the concentration of Al3+ is 5%, the green emission is enhanced by about 10 times, and the red light is enhanced by about 7 times. Obvious lattice shrinkage caused by the introduction of Al3+ is responsible for the enhancement. In addition, the optimal sample is highly thermally stable from 303 K to 443 K. The maximum relative sensitivity at 303 K increases from 0.791% K−1 to 1.106% K−1. The results indicate that NaBiF 4 : Er3+, Yb3+, Al3+ be a potential thermosensitive material. • Enhanced up-conversion luminescence and temperature sensing of NaBiF 4 : Er3+, Yb3+ is realized by Al3+ substitution. • Obvious lattice shrinkage caused by the introduction of Al3+ is responsible for the enhancement. • The optimized sample is highly thermally stable from 303 K to 443 K. • The maximum relative sensitivity is up to 1.106% K−1 at 303 K. [ABSTRACT FROM AUTHOR]

• The compact cascaded FPI fiber optic temperature sensors are proposed. • The sensor based on UV glue and HVE exhibits high sensitivities of 2.24 nm/°C. • Increasing the harmonic order of HVE improves the sensor's temperature sensitivity. • The sensors exhibits good linear response, excellent repeatability and stability. In this paper, compact cascaded Fabry-Perot interferometers (FPI) for fiber-optic temperature sensors are proposed and verified. The sensors are prepared by combining the properties of temperature-sensitive material ultraviolet glue (UV glue) and the basic principle of the traditional Vernier effect (TVE), first-order harmonic Vernier effect (HVE), and second-order HVE. The sensing cavity FPI s is made up of UV glue filling the gap between two single-mode fibers (SMF) with flat cut ends. The reference cavity FPI r is composed of SMF-capillary-SMF structure. The temperature sensitivity of the FPI s is up to 1.01 nm/°C by the high thermal expansion coefficient of the UV glue. By changing the free spectral range (FSR) of the FPI r , high detection sensitivities achieved are −10.14 nm/°C, 15.22 nm/°C, and 22.24 nm/°C, corresponding the situation of TVE, first-order HVE, and second-order HVE, respectively. The experimental results indicate that temperature sensors based on UV glue possess a simple and compact structure and strong resistance to electromagnetic interference, making them suitable for temperature measurement in various environments. [ABSTRACT FROM AUTHOR]

Mechanochemical has emerged as an eco-friendly, efficient, and upscalable tool for the synthesis of perovskite quantum dots (PQDs). However, achieving control over the size and ensuring good mono-dispersion of PQDs by mechanochemistry, while simultaneously increasing their stability remains a great challenge. Herein, we specifically chose a lead bromine-based MOF (PbBr-MOF) with [Pb 2 Br 3 ]+ nodes and utilized the uniform distribution of [Pb 2 Br 3 ]+ to induce the in-situ confined growth of Cs 4 PbBr 6 QDs via bottom-up mechanochemical approach for the first time, denoted as Cs 4 PbBr 6 @PbBr-MOF. The Cs 4 PbBr 6 QDs uniform and firmly anchor in PbBr-MOF through [Pb 2 Br 3 ]+ nodes, preventing their aggregation and enhancing quantum confinement effects. Highly dispersed Cs 4 PbBr 6 QDs (3.86 ± 0.61 nm) exhibit high photoluminescence quantum yield (31%) and notable durability in various solvents. Furthermore, Cs 4 PbBr 6 @PbBr-MOF demonstrates excellent performance as a temperature sensor, with maximum absolute (Sa) and relative (Sr) temperature sensitivities of up to 0.013 K−1 and 3.41% K−1, respectively. [Display omitted] • [Pb 2 Br 3 ]+ nodes in PbBr-MOF as Cs 4 PbBr 6 QDs precursors. • Enhancing Cs 4 PbBr 6 's confinement effect through controlled CsBr and nodes dispersion. • Cs 4 PbBr 6 QDs have 3.86 ± 0.61 nm size with high photoluminescence yield (31%). • PbBr-MOF boosts Cs 4 PbBr 6 QDs stability in harsh conditions. • Cs 4 PbBr 6 @PbBr-MOF shows impressive temp sensitivity. [ABSTRACT FROM AUTHOR]

Dual-emitting N-CDs with multi-application of white light emission, detection of metal ions, solvatochromism, detection of the water content in organic solvents, pH detection, and temperature detection. [Display omitted] • Dual-emissive N-CDs were synthesized and applied for pH and temperature sensing. • Ratiometric fluorescence probe based on N-CDs detected Fe3+, Cu2+ and Ag+ simultaneously. • N-CDs exhibited unique solvatochromism phenomena and were used for detecting water content in organic solvents. Ratiometric fluorescence probes based on multi-emission carbon dots improve accuracy and sensitivity on detecting various environment issues. Herein, a novel dual-emitting N-doped carbon dots (N-CDs) was synthesized from citric acid and urea via a solvothermal method in N,N-dimethylformamide (DMF). The blue and orange emissions of N-CDs in water were modulated, and pure white light-emitting with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.33) was achieved. The two PL centers behaved differently for Fe3+, Cu2+ and Ag+ ions, with the limit of detection (LOD) of ppm as fluorescence probes. Additionally, N-CDs displayed unique solvatochromism phenomenon. A new green emission appeared in organic solvents and gradually quenched with the increase of solvent polarity. The ratiometric PL displayed an excellent linear response for detecting water, and the LOD was between 0.003 % and 0.3 % in DMF, ethanol, isopropanol and N-methylpyrrolidone. Furthermore, N-CDs exhibited pH-sensitive response in the range of 4.0–7.0 and temperature-dependent response during heating–cooling cycles between 15 and 70 °C. A simple, efficient and reliable multi-functional ratiometric probe for detecting metal ions, water content, pH and temperature simultaneously was realized. However, there is a need for future application research to overcome the limitation imposed by the excitation wavelength of 330 nm. [ABSTRACT FROM AUTHOR]

In this paper, we first propose and demonstrate independently tunable dual Fano resonances based on a plasmonic structure composed of MIM (metal-insulator-metal) Sagnac loop with embedded Taiji resonator. An S-shaped crossover branch inside the Taiji ring resonator can tailor the propagating modes into their counter-propagating directions, finally tuning the number of whispering-gallery modes (WGMs) in Taiji resonator. Both Fano resonances originate from the interference between the discrete state generated from WGMs in Taiji resonator and continuous state from modes propagating in the plasmonic Sagnac loop. By stuffing a silver circle area (SCA) inside S-shaped branch, dual Fano resonances can be tuned independently as SCA has different sizes or locates at different places. Fano resonance would be influenced and shifted strongly when SCA locates at the energy intensity valley of WGM, while without any influence as SCA situates at the energy intensity peak of WGM. Thanks to the strong sub-wavelength light confinement of dual Fano resonances based on MIM plasmonic system, an optical refractometric sensor with figure of merit (FOM) of 100/RIU and high sensitivity of 1899 nm/RIU is demonstrated. Furthermore, this hybrid structure is also used for temperature sensing of ethanol with the maximal sensitivity of −0.793 nm/°C. This compact plasmonic Sagnac loop coupling Taiji resonator demonstrates impressive practical prospects for high-sensitivity biochemical sensors, nonlinear optics, and optical modulation. • Dual Fano resonances are observed and tuned based on MIM Sagnac loop coupling Taiji resonator. • Dual Fano resonances can be tuned independently in this hybrid system. • High-sensitivity refractometric sensing and temperature sensing are proposed, respectively. [ABSTRACT FROM AUTHOR]

• Simultaneous measurement of temperature, liquid level and axial strain based on torsional taper Mach-Zehnder interferometer with the Vernier effect is proposed. • A PMI is cascaded with a MZI to form the sensor with the Vernier effect. • PMI composed of PMF is less sensitive to environmental disturbance than MZI composed of TPSF. • The sensor with the Vernier effect magnifies the temperature, liquid level and axial strain sensitivities by 11.3, 11.2 and 12.6 times, respectively. A novel and simple highly-sensitive temperature, liquid level and axial strain sensor based on a torsional taper Mach-Zehnder interferometer (MZI) with Vernier effect is proposed. An interesting finding, which is the linear relationships between the wavelength shifts of resonance peaks (envelopes) and temperature, liquid level and axial strain surrounding the sensing fiber, is demonstrated experimentally. Another interesting feature is that the sensor with Vernier effect magnifies the temperature, liquid level and axial strain sensitivities by 11.3, 11.2 and 12.6 times, respectively. In the proposed method, the sensor is fabricated by cascading one polarization mode interferometer (PMI) as reference interferometer and one torsional taper MZI as sensing interferometer. The PMI is composed of polarization maintaining fiber (PMF), and cascaded MZI is composed of thin-core photosensitive fiber (TPSF). Combined with the characteristic of high sensitivity, the sensor can be widely used in the field of environmental and structural safety monitoring. [ABSTRACT FROM AUTHOR]

Ho3+-doped BaGd 2 O 4 phosphors sensitized by Yb3+ or Nd3+/Yb3+ have been prepared by solid-state reaction method. Almost pure green UC emission was obtained under 808 nm and 980 nm excitations. The green color purity of BaGd 2 O 4 : Yb3+/Ho3+/Nd3+ phosphor exceeds 93 % in the temperature range of 303 K–483 K under the excitation of 808 nm, indicating an excellent color purity and color stability. [Display omitted] • Strong green emission was obtained in BaGd 2 O 4 : Nd3+/Yb3+/Ho3+ phosphors excited at 808 nm and 980 nm. • The green up-conversion luminescence process of Ho3+ was insensitive to the doping concentration and sample temperature. • The temperature sensitivity of Ho3+ keeps constant in a wide temperature range. • BaGd 2 O 4 : Nd3+/Yb3+/Ho3+ phosphors exhibit high green color purity at different temperatures. Ho3+-doped BaGd 2 O 4 phosphors sensitized by Yb3+ or Nd3+/Yb3+ have been prepared by solid-state reaction method. The effects of concentration and temperature on the up-conversion (UC) luminescence properties and the temperature sensing behavior of the samples were investigated. Intense green UC emission at around 550 nm and weak red UC emission at around 675 nm were obtained under both 808 nm and 980 nm excitations. The relationship between the UC luminescence spectra measured at different temperatures and excitation power densities was analyzed. The results confirmed that the green UC emissions of Ho3+ are two-photon processes, which is insensitive to the sample temperature and excitation wavelength, while the red UC emission under 980 nm excitation is affected by temperature. In addition, the Judd-Ofelt intensity parameters of Ho3+-doped BaGd 2 O 4 phosphors were calculated by using the diffuse reflection spectra and fluorescence lifetime of Ho3+. By inspecting the temperature-varied fluorescence intensity ratio, the temperature sensing property of Nd3+/Yb3+/Ho3+ co-doped BaGd 2 O 4 phosphor under the excitation of 980 nm was investigated and a constant sensitivity was obtained to be 3.2 × 10−4 K−1 within the temperature range of 303–483 K. The green color purity of BaGd 2 O 4 : Yb3+/Ho3+/Nd3+ phosphor exceeds 93 % in the temperature range of 303 K–483 K under the excitation of 808 nm, indicating an excellent color purity and color stability. The results indicate that Ho3+-doped BaGd 2 O 4 phosphors sensitized by Yb3+ or Nd3+/Yb3+ have potential application in temperature sensors and luminescence imaging in complex environments. [ABSTRACT FROM AUTHOR]

• We develop a new SPR temperature fiber probe based on Au-PDMS@Au coating. • The probe has high sensitivity compared to conventional Au-PDMS probe. • The probe can be simply, rapidly and cost-effectively fabricated. • The probe has good repeatability and high mechanical strength. To enhance the sensitivity of polydimethylsiloxane (PDMS)-based optical fiber surface plasmon resonance (SPR) temperature sensing probes, we propose a new prototype with a PDMS@Au sensing layer on the gold (Au) film of the multi-mode fiber (MMF)-single-mode fiber (SMF)-MMF heterojunction structure. This designed probe has improved the temperature sensitivity from −1.26 nm/°C (Au-PDMS) to −2.14 nm/°C (Au-PDMS@Au), maintaining good repeatability and stability. Moreover, the probe can be fabricated with simple procedures at a low cost. Therefore, this probe is a promising tool for temperature sensing in various applications. [ABSTRACT FROM AUTHOR]

• A fiber temperature sensor based on cascaded FP cavities to achieve an optical Vernier effect. • The fiber temperature sensors achieved temperature sensitivities of 1.14 nm/°C, 0.29 nm/°C, and 0.19 nm/°C respectively. • The fiber FP cavities are uncomplicated and compact, and their use as sensing elements helps avoid temperature inhomogeneity. A fiber temperature sensor consisting of two cascaded reflective film-fiber-reflective film Fabry-Pérot (FP) cavities is proposed. The lengths of the two FP cavities are similar, but with small differences in their free spectral ranges (FSR) to create Vernier effect. The sensor operates similar to a Vernier caliper, where one FP cavity serves as a reference and the other as a sensing element. Experimental results demonstrate that the extinction ratios of cascaded system exceed 15 dB. The temperature sensitivity of the sensor reaches 1.14 nm/°C, offering advantages such as a wide measurement range, high sensitivity, good linearity, simple structure and low cost. Additionally, the fiber FP cavities are uncomplicated and compact, and their use as sensing elements helps avoid temperature inhomogeneity. This makes the sensor reliable, practical, and suitable for a wide range of applications. [ABSTRACT FROM AUTHOR]

The luminescent properties of main-group metal-organic frameworks (MOFs) can usually be modulated by organic ligands, and thus realizing temperature sensing over a wide range. Herein, a step-by-step decoration of hydroxyl groups on terephthalic acid (BDC) ligand was involved to regulate the excited-state intramolecular proton transfer (ESIPT) process of the ligands and thus the temperature sensing performance. Accordingly, the OH groups located on these ligands effectively regulate their luminescence sensing property with the absolute temperature sensing sensitivity following the order: DHBDC (0.62% K−1) > OHBDC (0.26% K−1) > BDC (no obvious linear relationship). Luminescent main-group MOFs with these ligands, namely MIL-53-Al-BDC/OHBDC/DHBDC and SNNU-301-Mg-DHBDC, were further selected to explore the temperature sensing performance. Thanks to the unique fluorescence characteristics of the DHBDC ligand, MIL-53-Al-DHBDC and SNNU-301-Mg-DHBDC both demonstrate excellent temperature sensing ability over a wide range (80–480 K) with the absolute temperature sensing sensitivity of 0.32% K−1 and 0.35% K−1, respectively. The compared luminescent spectra show that the stronger electron-donating ability of the substituents on the benzene ring can lead to the higher the electron cloud density in the MOF structure, and thus bring a higher temperature sensing sensitivity. This paper pays a new way for the exploration of practical wide-range MOF thermometers. [Display omitted] • Step-by-step regulation of ESIPT process by hydroxyl groups. • Main-group MOFs with ESIPT ligands. • MOFs with excellent wide-range temperature sensing performance. [ABSTRACT FROM AUTHOR]

• A new temperature sensing mechanism based on FIR between 5D 0 → 7F J (1, 2, 3, 4) and 5D 0 → 7F 0 transitions located in the orange-red region of Eu3+ ion was proposed. • Lattice distortion around Eu3+ ions caused by co-doped K+ ions resulting in enhanced sensitivity of temperature measurement. • The charge compensation effect of K+ ion significantly increases the luminescence intensity and efficiency of Eu3+ doped β-PbF 2 oxyfluoride glass ceramics. Eu3+ doped β -PbF 2 oxyfluoride glass ceramics (GCs) were synthesized via conventional melt-quenching method. The micro-morphology and luminescence properties of the fabricated GCs were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) spectra. A new temperature sensing mechanism based on fluorescence intensity ratio (FIR) between 5D 0 → 7F J (1, 2, 3, 4) and 5D 0 → 7F 0 transitions of Eu3+ ion was proposed. Such new mechanism is due to strong thermal coupling of 7F J (J = 0, 1, 2, 3, 4) states because of their small energy gap. With the increase of temperature, more and more population reaches high states 7F J (J = 1, 2, 3, 4) from 7F 0 state through thermalization process leading to different temperature-dependent transitions of 5D 0 → 7F J (J = 0, 1, 2, 3, 4). Furthermore, lattice distortion around Eu3+ ions caused by co-doped K+ ions resulting in distinct enhancement of emission of Eu3+ ion and violent splitting of 7F J (J = 2, 3, 4) states. Meanwhile, narrowing of energy gap between 7F J (J = 0, 1, 2, 3, 4) states resulting from the violent splitting of 7F J (J = 2, 3, 4) states facilitated thermalization process between 7F J (J = 0, 1, 2, 3, 4) states and then enhanced sensitivity of temperature measurement was obtained. We believe that this preliminary study will provide an important advance in exploring other innovative optical thermometry. [ABSTRACT FROM AUTHOR]

A twin-core sensor with high birefringence employing a photonic crystal fiber (PCF) is presented for simulated temperature measurements based on surface plasmon resonance (SPR). The internal wall of the central hole of the PCF is plated with gold and coated with graphene oxide (Au-GO) to develop an SPR sensing channel. The results of a numerical analysis with COMSOL Multiphysics show that the birefringence of this sensing structure can reach 0.0052. In addition, an average sensitivity of -12.695 nm/ °C can be achieved in the range of 0 °C~80 °C. Compared with uncoated GO sensors and existing sensing units, this sensor shows improved stability, sensitivity and birefringence.

Temperature-sensitive transient receptor potential (TRP) ion channels are members of the large tetrameric cation channels superfamily but are considered to be uniquely sensitive to heat, which has been presumed to be due to the existence of an unidentified temperature-sensing domain. Here we report that the homologous voltage-gated potassium (Kv) channels also exhibit high temperature sensitivity comparable to that of TRPV1, which is detectable under specific conditions when the voltage sensor is functionally decoupled from the activation gate through either intrinsic mechanisms or mutations. Interestingly, mutations could tune Shaker channel to be either heat-activated or heat-deactivated. Therefore, high temperature sensitivity is intrinsic to both TRP and Kv channels. Our findings suggest important physiological roles of heat-induced variation in Kv channel activities. Mechanistically our findings indicate that temperature-sensing TRP channels may not contain a specialized heat-sensor domain; instead, non-obligatory allosteric gating permits the intrinsic heat sensitivity to drive channel activation, allowing temperature-sensitive TRP channels to function as polymodal nociceptors.

For achieving well-performing optical thermometry, a new type of dual-mode optical thermometer is explored based on the valley-to-peak ratio (VPR) and fluorescence lifetime of Eu3+ emissions in the ZrO2:Eu3+ nanocrystals with sizes down to 10 nm. In the VPR strategy, the intensity ratio between the valley (600 nm) generated by the emission band overlap and the 606 nm peak (5D0→7F2), which is highly temperature sensitive, is employed, giving the maximum relative sensing sensitivity (Sr) of 1.8% K−1 at 293 K and good anti-interference performance. Meanwhile, the 606 nm emission exhibits a temperature-dependent decay lifetime with the highest Sr of 0.33% K−1 at 573 K, which is due to the promoted nonradiative relaxation with temperature. These results provide useful information for constructing high-performance dual-mode optical thermometers, which may further stimulate the development of photosensitive nanomaterials for frontier applications.

Abstract A novel fiber inline Mach-Zehnder interferometer (MZI) is proposed for simultaneous measurement of curvature and temperature. The sensor composes of single mode-multimode-dispersion compensation-multimode-single mode fiber (MMF-DCF-MMF) structure, using the direct fusion technology. The experimental results show curvature sensitivities of −12.82 nm/m−1 and −14.42 nm/m−1 in the range of 0–0.65 m−1 for two resonant dips, as well as temperature sensitivities of 57.6 pm/°C and 74.3 pm/°C within the range of 20 °C–150 °C. In addition, the sensor has unique advantages of easy fabrication, low cost, high fringe visibility of 24dB, and high sensitivity, which shows a good application prospect in dual-parameters of sensing of curvature and temperature.

In this article, a refractive index sensor based on Fano resonance, which is generated by the coupling of a metal–insulator–metal (MIM) waveguide structure and a toroidal cavity with a built-in elliptical ring (TCER) structure, is presented. The finite element method (FEM) was employed to analyze the propagation characteristics of the integral structure. The effects of refractive index and different geometric parameters of the structure on the sensing characteristics were evaluated. The maximum sensitivity was 2220 nm/RIU with a figure of merit (FOM) of 58.7, which is the best performance level that the designed structure could achieve. Moreover, due to its high sensitivity and simple structure, the refractive index sensor can be applied in the field of temperature detection, and its sensitivity is calculated to be 1.187 nm/℃.